Hi Grant,

FWIW, at an earlier job location, we had jsut about finished qualifying
Interflux no-clean flux for wavs soldering. We couldn't detect visible residuye
after wave. Their hand soldereing cored solder was a different matter. Thjis was
about 4-5 years ago. I'm sure there have been many improvements on the part of
all the flux makers.

In the area of solderballs, one thing that will help reduce solderballs is being
absolutly certain that all solder paste goes on the pads and NOT ON THE BOARD!
For me, this mean getting slightly wider that "normal" pads on our .5mm pitch
parts. It also means that any mis-printed boards need to be cleaned very
thoroughly. You pretty much need a stencil cleaner with a board holder
attachment. Even though some thing is "no-clean" it doesn't mean that cleaning
goes completely away  : > {

Good luck

Charlie B.




Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to
      Grant Emandien <[log in to unmask]>








 To:      [log in to unmask]

 cc:      (bcc: Charles Barker/US/I-O INC)



 Subject: [TN] Solder/Flux/ICT Issue








Hi again,
Thanks for all the input as it has now directed me towards fluxes (and
control thereof) and ICT.
Leading from one of the members advice of low residue flux I stumbled across
this Kester comment:
'Flux selection does have some play as to the occurrence of solder balls. A
rule of thumb is that the lower the solids content of the flux is the more
solder balls will be noted when all other parameters are held constant. This
is sort of a dilemma for us as a flux manufacturer in that if we increase
the solids content, we will more than likely have an adverse impact on probe
testing of final soldered assemblies. The aesthetics of the final soldered
assembly will also be affected as you can imagine.'  This was posted in 1993
so any idea on what has since transpired and is this statement still valid
wrt the solids content?
Geez, my research thusfar has brought an array of variables to this party
such as test pin profiles and type, gold plating vs gold alloy, pin base
material hardness, spring force etc. on the ICT aside. Nevertheless it is
now beginning to get interesting.
As a comment, I hope my research drives me away from introducing another
process i.e. cleaning of assemblies hence and control of flux effluent (we
are coincidentally reviewing ISO14000) etc. and rather focus on improving
the existing process i.e. flux residue reduction (without cleaning) and ICT
issues.
Thanks again to all,
Grant

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